How coral larvae travel thousands of miles due to climate change

Washington: A new computer simulation has revealed the epic, ocean-spanning journeys travelled by millimetre-sized coral larvae through the world`s seas.

The study, conducted at the University of Bristol (UB) and University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science, is the first to recreate the oceanic paths along which corals disperse globally, and will eventually aid predictions of how coral reef distributions may shift with climate change.

Coral reefs are under increasing threat from the combined pressures of human activity, natural disturbances and climate change.

It has been suggested that coral may respond to these changing conditions by shifting to more favourable refuges, but their ability to do this will depend on the ocean currents.

"Dispersal is an extremely important process for corals. As they are attached to the seafloor as adults, the only way they can escape harmful conditions or replenish damaged reefs is by releasing their young to the mercy of the ocean currents," Sally Wood, a Ph.D. candidate at UB, said.

Where these intrepid explorers end up is therefore an important question for coral reef conservation.

However, tracking the movement of such tiny larvae in the vast oceans is an impossible task.

Collaborating across the pond, Wood used the Connectivity Modeling System (CMS) developed by Dr. Claire Paris, associate professor of Applied Marine Physics at UM to identify the billions of paths taken.

This larval migration model had been tested in a previous study against the reef-building coral Montastraea annularis in the Caribbean, where consensus between modeled estimates of genetic structure were found.

Some of the results yielded by the team were surprising. While the majority of simulated larvae settled close to home, others travelled as far as 9,000 km., almost the entire width of the Pacific Ocean.

When considered over multiple generations, this means that corals are able to cross entire ocean basins, using islands and coastlines as "stepping stones."

The study is published in the journal Global Ecology and Biogeography.